1. Field of Invention
The present invention relates to a tempering device for laboratory vessels and including a liquid-tight housing filled at least partially with a tempering medium and in which inwardly pointing depressions are formed.
2. Description of the Prior Art
Generic tempering devices, which are also referred to as cooling accumulators or the like, are used to temper laboratory vessels, such as reaction vessels containing heat-sensitive liquid batches.
Generic tempering devices have a liquid-tight housing, which is filled at least partially with a tempering medium such as water. Before use, the tempering devices are heated or cooled and are then in a position to maintain the temperature within a certain range for a longer period of time (up to a few hours).
An example of a generic tempering device is disclosed, e.g., in German Utility Patent G 92 05 100.6. The device described here is used, for example, together with a holder, in which the reaction vessels are accommodated with their closed ends freely hanging downward. The housing of the tempering device has depressions to the number and arrangement of which correspond to the holes of the holder. In operation, the holder is disposed on the tempering device in such a manner, that the reaction vessels, which are accommodated in it, are inserted with their closed ends in the depressions of the tempering device. Independently of this, however, the reaction vessels can also be inserted directly, that is, without holders, in the tempering device.
A drawback of the known device consists in; that it is difficult to check whether or not the device still makes possible the desired tempering within the range of the required working temperatures.
Accordingly, it is an object of the present invention to provide a tempering device for laboratory vessels such that a user can easily check its temperature state.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by forming the housing of the tempering device at least partially of a plastic dyed with a heat-sensitive dye.
Heat-sensitive dyes, which can be used to dye the housing or regions of the housing of the inventive tempering device, have been known for a long time. Usually, they can have two different colors, which depend on the temperature, with the color change taking place reproducibly in a temperature range, specific for a respective dye.
For the inventive tempering devices, which are to be used primarily for cooling purposes, especially those dyes are suitable, which change their color just above the freezing point, that is, in a range between 4xc2x0 and 8xc2x0 C. If a color change occurs during use, then this is an indication of the abating cooling performance of the tempering device.
The known heat-sensitive dyes are used already for a series of different applications. For example, there are plastic spoons, which are included in packages of cornflakes and change their color depending on the temperature. Further applications are to be found in the fashion jewelry sector. However, until now, the use of heat-sensitive dyes remained limited to everyday objects or the advertising sector. Uses in the research area or in the laboratory area are not known.
It is conceivable that individual, well recognizable regions of the housing of the inventive tempering device are dyed with heat-sensitive plastic. However, it is also, of course, possible to produce the whole housing of a plastic, appropriately dyed with a heat-sensitive die. The manufacture may take place in the usual manner, for example, by injection molding.
The inventive tempering device offers a series of advantages. It is an important advantage that the user be informed in a clearly recognizable manner, for example, of the abating cooling performance of the tempering device and optionally, in the case of an appropriate configuration, even receives individual information concerning the temperature of individual laboratory vessels placed in the device.
All the usual media, suitable for tempering, can be used in the inventive tempering device. Advantageously, the phase transition of a tempering medium, contained in the tempering device is utilized for the tempering. For example, it is conceivable to provide a medium based on water and ice or the like, which is suitable for tempering low temperatures (cooling effect). Tempering devices with such cooling media are cooled before use up to solidification. During use, the medium is heated relatively rapidly up to its melting temperature and then maintains this value. A constant cooling effect is achieved in the region of the melting temperature of the tempering medium, which decreases with increasing conversion to the liquid phase.
It is, of course, also possible to provide other tempering media, especially those, which make a constant temperature possible in the physiologically interesting region between 25xc2x0 C. and 37xc2x0 C. Here also, media can be used once again, the solidification or melting temperature of which corresponds to the desired working temperature. In this case, the tempering elements are heated before use to a temperature above their melting temperature. During use, the tempering medium changes from a liquid to a solid aggregate state, this process extending over a longer period of time, in which the stored energy is given off slowly and uniformly and the temperature remains stable (in the region of the solidification temperature).
In both cases, the duration of the tempering effect depends primarily on the insulation of the tempering device from its environment. In the case of the inventive tempering device, it is a further problem that the housing, and the heat-sensitively dyed regions contained therein, have direct contact with its surrounding environment, unless other provisions are made. The danger therefore exists that a change in color of the regions occurs, which is produced by the temperature of the surrounding environment and does not correspond to the actual cooling state of the device and, especially, not to the actual cooling state of interest in the depressions. In this connection, a particularly preferred development provides that only the wall regions, adjoining the depressions, are produced from the heat-sensitive plastic or, since such a production is relatively expensive, in the case of a housing consisting, as a whole, of heat-sensitive plastic, a cover, covering or insulating at least its upper surface, is provided, which has a window assigned to the depressions. In the case of this development of the housing, the actually interesting information, namely, the temperature state in the depressions, can be recognized particularly easily.
According to a further advantageous development of the invention, the housing is thermally insulated from the outside. The insulation may be transparent as a whole. It is, however, also possible to make the insulation opaque and to provide a window in the insulation, which is assigned to the selected regions of the housing, as described, for example, above.
In this connection, it would be conceivable, for example, that the tempering device is accommodated in a further insulated housing, which is open at one side and inverted before use over the pre-tempered device. Equally well however, it would also be conceivable to provide thermally insulating coatings or components at the outer regions of the housing. For example, it would be conceivable to dispose pockets at the outside of the housing, into which the optionally transparent plastic plates with insulating properties can be inserted.
As stated above, a significant advantage of the inventive tempering device consists in that, by a change in color of the heat-sensitive region or regions of the housing, it is possible to check rapidly and in a simple manner whether the temperature state of the device is still in the desired working temperature range.
Advantageously, the tempering medium and the heat-sensitive plastic, used to produce the inventive tempering device, should be coordinated to the desired tempering range. The tempering medium should be selected so that, after an appropriate pretreatment, a temperature in the region of the desired working temperature range is maintained over a long period of time. The heat sensitive plastic, on the other hand, should be selected so that its changeover temperature is somewhat below or above the desired working temperature region, depending on whether the tempering device heats up or cools off during the work due to the temperature of the surroundings.
Aside from an indication concerning the general temperature state of the device, it is, however, also of interest to know the temperature of the individual laboratory vessels, tempered by the device. For example, it is conceivable that vessels with different initial temperatures are inserted into the tempering device, after which they are to follow a common further processing only when all the vessels have been cooled down, for example, to the desired working temperature range.
For these or similar cases, according to the invention the depressions of the tempering device are provided with protruding regions, which are dyed with a heat sensitive dye and are in direct thermal contact with the inserted laboratory vessels. Because of their distance from the remaining wall regions of the depression, which are in direct contact with the tempering medium and therefore do not change color as rapidly, these regions, which may be constructed, for example, in the form of protruding ribs, are in a position to indicate individually the temperature of the inserted laboratory vessels and permit a rapid conclusion to be drawn concerning the progress of a cooling or heating process. In addition, ribs, for example, represent a guidance for the vessels and, because of the reduced heat transfer, can prevent the freezing of the contents of vessels in the depressions.